In 2008 I got a help email from a friend with a similar problem -- only he was already on the ground in a 230v country. As I was struggling with a fix, it occurred to me that the shaver outlets in most 230v bathrooms can handle low amperage 110v (making sure that the switch is in the correct position). My friend did that and it worked like a charm.

I wouldn't worry about a one time use charger. If you want a charger for your your phone hit Amazon or Ebay and you can probably find a permanent one for $10.

Alternatively go to front desk at 11:30pm telling them that you lost your charger. Most hotels have a box of chargers that customers have left behind and half the time they will let you pick through it without any excuse at all.